The present invention relates to a waterproof sheet and a process for the manufacturing thereof.
Waterproof products employed when a protection from water is needed, are known in the state of the art; some of said products are, for example, bituminous membranes, sheets made of PVC, sheets made of rubber, etc.
Bituminous membranes are manufactured by immersing frameworks, among which are polyester spunbonded fabrics, in a bath of bituminous mixture which is warm enough to obtain, after cooling, rolls displaying a height of approximately 1 meter, a length of approximately 10 meters and a weight varying from 350 g/sqm to 5 kg/sqm and greater. The laying occurs by unwinding the roll of membrane on the surface to waterproof, inducing it to adhere mainly by means of flame-hardening of the back with a flame blow-pipe, in order for the slightly molten part to attach to the surface. Another membrane roll is unwound in parallel to the first one taking care to overlap it by a width of at least 5 cm. The overlapping part is flame-hardened and pressed along the contact line in order to link the two layers of membrane. The critical part is the junction area between the rolls, which may allow the penetration of water if not properly manufactured.
The membranes made of PVC are synthetic sheets obtained by extrusion of “polyvinil chloride” polymer. Generally commercially available rolls have a height even taller than one meter, lengths of 15-20 m and different thicknesses. The roll is stretched out on the surface and another roll is stretched out in parallel to the first taking care to overlap it by a width of a least 10 cm. The overlapping part is linked by means of a chemical compound which fuses the PVC on the surface or by means of a hot air gun that melts and links the overlapping edges, by exploiting the low melting point of the PVC. An inert layer is normally deposited on the PVC layers, having the function of makeweight, in order to allow the attachment of the PVC membrane to the surface. A possible penetration of water, caused by poor junctions, does not remain restricted to the penetration spot and instead spreads under the cover.